Maybe they require some understanding and appreciation of history and that is also sort of out of vogue now?
Yes, I would agree with you.
Most movies today are adaptations or sequels. Studios look for their next big 3-movie franchise that is going net them over a billion $$$ worldwide, and it's pretty hard to sell a WW2 or any historical film as such.
I think there is an appetite for these types of movies. Saving Private Ryan was a hit. Pearl Harbor, while it wasn't very good, made money. Even Valkyrie and U-571 were WW2 movies that made their money back. Gladiator, Braveheart, Black Hawk Down, these war movies don't lose money.
It just seems to me to be an untapped market. And it seems clear the studio releasing Red Tails isn't too optimistic about it thus why it's getting released in January, as opposed a few months later or after. January and September are the two lowest-grossing movie months in Hollywood. It's not exactly "dumping" a film, but it's certainly not giving it the best chance to succeed.
Hollywood is a copycat. We'll see more of these movies once somebody makes a hit. I don't think that's going to be Red Tails, but it's at least a step in the right direction.